1.Easy
Two point charges repel each other with a force of 42 N. The first charge is halved and the distance between the charges is made four times as large. Find the new force F′.
F = 42 Nq₁′ = 0.5·q₁r′ = 4·r
F′ = N
Coulomb’s law & electric fields worksheet with answers
2.Easy
Two point charges of −1 µC and +2 µC are 15 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².
q1 = −1 µCq2 = +2 µCr = 15 cm
F = N
3.Medium
Two identical small metal spheres carry charges of −1 µC and −2 µC. They are touched together and then put back 10 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².
q1 = −1 µCq2 = −2 µCr = 10 cm
F = N
4.Medium
Three point charges lie on a straight line: −4 µC on the left, −3 µC on the right 30 cm away, and +8 µC between them, 12 cm from the left charge. Find the magnitude of the net electric force F on the middle charge. Use k = 8.99 × 10⁹ N·m²/C².
qL = −4 µCqR = −3 µCqM = +8 µCrL = 12 cmrR = 18 cm
F = N
5.Hard
An electron enters the uniform field between two parallel plates moving parallel to them at 3 × 10⁷ m/s. The plates are 5 cm long and the field between them is 4900 N/C. Electron charge 1.602 × 10⁻¹⁹ C, mass 9.109 × 10⁻³¹ kg; ignore gravity. How far y is it deflected sideways when it leaves the plates? Give the answer in mm.
v₀ = 3 × 10⁷ m/sL = 5 cmE = 4900 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm
6.Hard
Three positive point charges sit at the corners of a right triangle: q₃ = 1 µC is at the right-angle corner, q₁ = 1 µC is 6 cm from it along one side and q₂ = 8 µC is 6 cm from it along the other side. Find the magnitude of the net electric force F on q₃.
q1 = 1 µCq2 = 8 µCq3 = 1 µCr13 = 6 cmr23 = 6 cm
F = N
Answer key
- 1. F′ = 1.313 N
- 2. F = 0.7991 N
- 3. F = 2.023 N
- 4. F = 13.32 N
- 5. y = 1.197 mm
- 6. F = 20.13 N
Full step-by-step solutions: practise this topic on examproblems.com.